I would say that the correct answer is B, although the elimination process is a bit tricky, because the errors are hard to describe - they are mostly issues of "diction" - the choice of the appropriate words.

A - the original sentence is flawed for two reasons. Rhetorically, we expect the adverb "so" to be repeated before "reflective". Otherwise the logic of the argument does not come across. In addition, the adverb "otherwise" is awkward and doesn't convey the proper meaning. "Otherwise" means, "under other circumstances" - but the hard facts of cold temperatures and reflective ice are not truly variable circumstances in the standard sense.

C omits the parallel 'to be' verb before "cold" which is problematic as a parallel construction: it is awkward to mentally carry over the plural "[temperatures] are " to match [the ice cap (is) so reflective". Furthermore, the conjunction "or else" is also inappropriate, in much the same way as "otherwise" does not work here, rhetorically.

D - like A, "so" is missing. D also uses the wrong conjunction, creating a flawed parallelism - "or" would be correctly used to present viable alternatives, however, this sentence contrasts a real situation with a hypothetical situation - these are not viable, realistic alternatives.

E - does use a conditional, to indicate a hypothetical alternative, but the beginning of the underlined section is no good. We need a phrase to parallel "so cold" and "reflects" is a verb, not an adjective.

This leaves us with B - which gives us the expected parallel construction "so cold // so relective". It also conjoins the two clauses more effectively by using the hypothetical conditional - were it (=the polar ice") to melt....

I agree with B.

I disagree with C because it says little polar ice melts. As in little/baby/or that the polar ice is small, and that small polar ice is what melts. The sentence is saying that little of the polar ice melts.

Couple thoughts on this one:

1) I've seen this question in a few different forms in different forums over the last few years, so it may have been tweaked and skewed over time. One had B as "were it not to do so", for example.

2) B is wrong. That phrase "were it to do so" doesn't fit: "it" could refer to "Antarctica" as the subject of the sentence or to "polar ice" as the subject of the subordinate clause right before it. So that's potentially pretty ambiguous. But even if we accept that it refers to "polar ice", note that it doesn't make sense to say "were it to do so" when the previous clause says, in fact, that it does so!!!! The previous clause says "polar ice melts" (well, little of it) - so there's no juxtaposition between "it doesn't...but if it did". We already said that it does! So there's no justification for giving that counterpoint - it's not a counterpoint.

So I want to make sure to at least point out that huge flaw in B. B is not a good answer choice.

Agree B sounds like crazy but B is still close..